SD Card Slot
The SD card slot is housed in a small compartment on the front of the Wii console. To insert an SD card into a Wii, turn the power off, open the door to the compartment and place the card into the slot with the label facing the Wii's game disc drive.
Compatibility
Your Wii's firmware, called the Wii Menu, determines the maximum size of SD card that you can use with the console. Consoles with Wii Menu 4.0 or later can use SD cards up to 32 GB in size. Wiis with earlier versions of the system software may not be able to utilize cards greater than 2 GB. To check your Wii Menu version, turn on your Wii, press the "Wii" button in the lower-left corner of the screen, and choose "Wii Settings." The version number appears on the top-right corner of the screen.
Saving to the SD Card
When you download a WiiWare game, you're asked where you'd like to save the data. Choose the SD card option to download directly to that storage device. If you'd like to transfer existing WiiWare games from your Wii's hard drive to the SD card, press the "Wii" button on the main menu, then select "Data Management." Choose "Save Data," then select "Wii." Choose the game you'd like to move to the card, select "Copy," and then "Yes" to confirm the transfer.
Launching Games from an SD Card
Wii Menu 4.0 includes an SD Card Menu, which appears next to the "Wii" button on the lower left of the screen. Select this menu from the Wii's main screen to view the contents of the SD card. Your card can hold up to 240 items, including WiiWare games, Virtual Console games and Wii channels. Choose a WiiWare game from the list, press the "A" button, and then select "Start."
Considerations
The Wii console's hard drive isn't very large, so SD cards can be used to free up space on the internal drive. WiiWare games downloaded or moved to an SD card can only be played on the console on which they were originally downloaded. Some WiiWare games with online play may not be able to launch from an SD card. While a game can reside on an SD card, the saved game files must be saved to the Wii's hard drive.